Busk (1854) described Lepralia cucullata from the Aegean Sea and noted that, owing to the absence of ovicells, it was not possible to assign his specimens to Savigny’s species (Savigny 1817, pl. 8, fig. 6), which had been named Cellepora mangnevillana Lamouroux, 1816 by Audouin (1826). The species was characterized by a black colouration and a granular surface (Busk 1854), and Waters (1879) described frontal pseudopores in Busk’s specimens as well as his own colonies from Naples. Hincks (1886) used the name Schizoporella atrofusca Busk, 1856 for the specimens reported by Waters (1879) and included the form labiosa from the Arabian Sea, but gave no additional accounts of Busk’s types of L. cucullata or S. atrofusca. Waters (1909) and Hastings (1927, 1930) also included S. atrofusca under L. cucullata, but their description encompassed more than one species (see also Soule & Soule 1975). Harmer (1957) synonymised three species— Cellepora subtorquata, Lepralia cucullata and Schizoporella atrofusca —under Watersipora subovoidea (as Dakaria subovoidea), which contrasts with the statement of Hastings (1930), who suggested the existence of more than one species under the name Watersipora cucullata; nevertheless, Hastings did not introduce new names for specimens with distinct opercular shapes. Mawatari (1952), however, introduced the variety watersi for specimens reported by Waters (1909) and Hastings (1930), which may represent at least two distinct species (see below).

Following examination of the type specimens of Busk’s L. cucullata —i.e. Watersipora cucullata, NHMUK 1854.11.15.189, lectotype (Figs 6–9), chosen by Soule & Soule (1975), plus NHMUK 2012.6.30.1, paralectotype (Figs 25–29)—and S. atrofusca —i.e. Watersipora atrofusca, NHMUK 1892.9.6.4 (Fig. 10)—we conclude that these should be considered as distinct species, as was suggested by Soule & Soule (1975). Orifice size in the two species differs, being larger in W. cucullata than in W. atrofusca. Two small latero-oral multiporous septula in the frontal shield (equivalent to the ‘intrazoidal septula’ of Banta 1970, p. 39), one on each side of the orificial sinus, are present in W. cucullata (Figures 8, 29) but are lacking in W. atrofusca. Watersipora subtorquata is distinguished from Busk’s W. cucullata by the shape of the orifice, the shape and size of the condyles, and the size of the frontal pseudopores. Ryland et al. (2009) considered the identity of Busk’s W. cucullata “clear”, following the descriptions of Hastings (1930), but Hastings mentioned a distinct variety among her specimens, as noted in her description and plates (Hastings 1930, p. 730, pls 102–104).

Ryland et al. (2009, p. 53) attempted to solve nomenclatural problems concerning W. subovoidea and to stabilise d’Orbigny’s species name by designating Busk’s type of W. cucullata as the neotype of d’Orbigny’s W. subovoidea, thereby making Watersipora subovoidea the senior synonym of Watersipora cucullata. Unfortunately, the descriptions and figures of W. subovoidea in Ryland et al. (2009) are actually of W. subtorquata (see above). Furthermore, the selection of a neotype for W. subovoidea from a site (Aegean Sea) distant from the type locality (Egyptian Red Sea) is contentious. According to the ICZN (1999, Article 75.3.6) evidence should be provided that the neotype came as nearly as practicable from the original type locality, which was not provided in the Ryland et al. (2009) paper. Thus, Cellepora subovoidea d’Orbigny, 1852 is here considered a nomen dubium.

Below we provide redescriptions of d’Orbigny’s species W. subtorquata and W. cucullata and reassign the species erroneously identified as Watersipora subtorquata by Ryland et al. (2009) to a third species previously described by Ortmann (1890) under the name Schizoporella aterrima var. subatra (= Watersipora subatra, see below). We also describe two new species: Watersipora mawatarii n. sp. from Japan, and Watersipora souleorum n. sp. for specimens from Cape Verde and Naples previously assigned to Watersipora cucullata.